Devices for measuring wind velocity have been known for many years. The two most common devices used for this measurement are the wind vane and the anemometer. The wind vane is used to indicate wind direction and typically comprises an asymmetrical marker which is horizontally mounted on a vertical rotating shaft. The bulk of the area of the marker lies on one side of the vertical shaft. The marker is free to rotate so that it assumes a direction parallel to the flow of the surrounding air. The anemometer measures wind speed and typically consists of a plurality of hemispherical cups, each mounted at the end of an arm. The arms are radial members which rotate about a vertical central shaft. The speed of rotation is proportional to the wind speed.
The prior art produced many methods of retrieving electronic measurements of wind velocity from remotely located fluid velocity transducers. U.S. Pat. No. 2,600,011 to MacDonald, et al. features a device for measurement of fluid flow within a pipe or conduit. A twisted vane is mounted inside the pipe so as to rotate around the pipe's longitudinal axis with a speed proportional to fluid flow. A permanent magnet is disposed in a direction parallel to the pipe's longitudinal axis. The magnet is mechanically fixed to the vane with a radial displacement slightly less than the pipe's radius. A reed switch is situated just outside of the pipe, in a direction parallel to the magnet. The reed switch includes a pair of contact members which form a closed circuit path in the absence of substantial magnetic flux from the permanent magnet. When fluid flow actuates the vane, the magnet will periodically rotate to a position near the reed switch, causing the switch to open and close. By measuring the frequency with which the circuit opens, the fluid speed is measured.
U.S. Pat. No. 3,282,099 to Kingman features a wind speed and direction transducer in which a first reference marker is fixed on the rotating member of an anemometer and passes a first sensing means once each revolution. The first sensing means is disposed at a first angular disposition, fixed with respect to the axis of rotation (e.g., directed towards true north), to sense the first reference marker. The delay between successive passes of the first reference marker over the first sensing means provides a measure of wind velocity.
A second reference marker is fixed to a wind vane, and thus is oriented in the direction of the wind azimuth. A second sensing means is provided for sensing coexistence of the first and second reference markers at a single angular position. Circuit means are provided which serve to relate the elapsed time between sensing the first reference marker at the first disposition and at the second angular disposition for comparison to the elapsed time between the sensing of the first reference marker at the first angular position twice in succession. This provides a measure of the angular displacement between the wind azimuth and the fixed first reference marker.
The sensing means is provided by the use of an air dielectric capacitor arranged so that the two plates of the capacitor rotate with respect to one another once per revolution of the transducer. The plates are closely spaced and are formed and positioned so as to provide minimum and maximum capacitance values during each revolution of the transducer about its axis. This periodic variation in capacitance is used to provide an output signal having an amplitude proportional to the speed of rotation.
Kingman also features an alternate embodiment for sensing the speed of rotation in which the anemometer drives a rotating disc. The disc includes a plurality of fingers which pass between the pole pieces of a ring-type or other magnetic core. The core is energized to provide a magnetic flux between its two pole pieces. The fingers are of a highly permeable material so as to cause detectable variations in the magnetic flux field between the pole pieces.
U.S. Pat. No. 3,364,740 to Wong features a wind vane in which there is provided a permanent magnet fixed to rotate about the axis of rotation of the vane, such that the permanent magnet will always align with the direction from which the wind is blowing. A plurality of reed switches are provided in a circle concentric to the permanent magnet. The spacing between the circle of reed switches and the permanent magnet is such that the reed switch facing in the direction of the wind will be actuated by the magnet.
U.S. Pat. No. 3,420,101 to Adams features a wind vane and an anemometer mounted on separate, independently rotating shafts. The anemometer shaft rotates a disk on which are located two sets of indices. The first set of indices produces a pulse each time an index passes over a fixed pickup, to provide a measure of wind speed. There is a second fixed pickup and also a moveable pickup, attached to the wind vane shaft. A wind direction measuring interval is defined by the coincidence of the second set of indices with the second fixed pickup and the moveable pickup. The number of pulses by the first set of indices during this interval defines the wind direction. In Adams, each pickup includes a small ferrite core energized by high frequency AC current.
U.S. Pat. No. 3,713,336 to Bernstein features a transducer with a reed switch mounted to a rotating shaft upon which is mounted a wind vane, so that the switch points in the same azimuthal direction as the vane. A permanent magnet is fixed to a rotating anemometer shaft concentric to the reed switch, and at the same height as the switch. The reed switch is activated to produce an electrical signal each time the permanent magnet passes the reed switch.
Also positioned in the anemometer is a magnetic field responsive electric device, such as a magnetodiode, which has an electrical characteristic that changes in response to the magnitude and polarity of the magnetic field to which it is exposed. The magnetic field responsive device is connected in an electric circuit which produces a signal proportional to both the magnitude and direction of the earth's magnetic field and also to the speed of rotation of the anemometer.
Both the output signals from the wind vane and the anemometer have frequencies equal to the frequency of rotation of the anemometer. They differ in phase by an amount which is proportional to the angular displacement of the wind vane from a fixed direction (e.g., true north).
U.S. Pat. No. 4,548,074 to Krueter features an apparatus for measuring wind speed and direction comprising two electrical coils which produce respective electrical signals that are utilized to indicate the wind direction, and an anemometer which rotates actuators through signal producing gaps of the coils. The gap of the first coil is defined by a fixed tang, and the gap of the second coil is defined by a movable tang positioned by a wind vane.